Voltage regulated power supply



1956 H. H. MARTIN 2,758,273

VOLTAGE REGULATED POWER SUPPLY Filed Oct. 16, 1-953 Inventor-z H ugh H.Martin Hig ftorhe.

United States Patent VOLTAGE REGULATED POWER SUPPLY Hugh H. Martin,Syracuse, N. Y.', assignor to General Electric Company, .a' corporationof New York Application October '16, 1953, Serial No. 386,590

Claimst (Cl. 323 -22) trol amplifier electric discharge device sensitiveto changes in output voltage foraltering the resistance of the varialeresistance device to maintain the'output voltage'constant. In such aregulator, the anode voltage of the control amplifier discharge deviceis usually obtained from the output voltage of the supply. When such aconnection is made, the available anode voltage is always less-than thatavailable from the direct current supply, andwhen low output voltagesare developed, thereduction in 'anode-v0lt' age may considerably reducethe gainof thecontrol amplifier device, thereby reducing-the accuracyofregulation and making it dependent on'the magnitude of the-output.

voltage.

Warm-up protection is a second problem arising in regulated powersupplies. In most applications, the electric discharge devices employedas-variable'resistances have relatively highcurrentheatershaving'relatively'short warm-up periods while the electric-dischargedevices employed as the control amplifiers havelow current heatershaving somewhat longer warm-up periods. As a result of'thisdifterenceinwarm-up time, there is a short period during which thevariable resistance device is "fully conductive'but not under the.control ofithe control discharge devices which are not yet conductive;Laclcofcontrol duringthis period usually results in a soaring potentialat the output of thevoltage regulator. This effect-shortens the lives ofcomponents in the load designed forlower op crating voltages.

Accordingly, it is an object of the presentainvention to provide animproved .voltage regulator circuit' inwwhich the accuracy of controlisindependent ofoutput voltage and in which the output voltage ismaintained'at a reduced value during the warm-up period.

Another object of this invention is torprovide'a voltage regulator ofthe type havinga variable resistance. electric discharge device andanamplifier control electric. discharge device in which the gain of theamplifier discharge device is independent ofthe'condition:of'conductivity of the variable resistance deviceandinwhichthe variable resistance device. There .is further provided atime delay" circuit including a pair ofzresistances a.capacitance, and.a gaseous discharge device, saidelementsbeing arranged- 2,758,273Patented Aug. 7, 1956 The novel features which are'believed to becharacteristic. of this invention are set forth with particularity inthe appended claims. The invention, however, both as to its organizationand method ofoperation, together with further objects and advantagesthereof," m'aybest' be understood by reference tothe'followingdescription taken in connection with the accompanyingschematic drawing.

Referring now to the drawing, there is shown a regu lated-power supplycomprising a direct current source 1, output terminals 2 for connectionto a load 2a, a variable resistance discharge device 3, forconveniencetermed a variable resistance hereafter, a control voltageamplifier discharge device 4, for convenience termed a. controlamplifier hereafter, and a time delay circuit. The variable resistance3, having an anode 5, a cathode 6, and a control grid 7 is connected inseries between 'thesource 1 of direct current voltage'and theout-put'terminals 2, the anode 5 being connected to the positiveterminals or" the di-.

rect'current source, the cathodeo being connected to one.

of the output terminals andthe control grid '7 being c011- nected to theoutput of the control voltage amplifier 4.

The control voltageamplifier l is shown as a pentode having an anode, acathode-and three: grids. The anode 3 of the control voltage amplifieris directly connected to the grid 7 of the variable resistance deviceandthe anode 8 is further connected through a load'resistor 9 to thepositive terminal of the direct current source 1. The cathode 10 of thecontrol amplifier 4is connected to a source of stabilized direct currentpotential comprising a voltage regulator discharge device 11; a firststorage capacitor 12; a resistor 13, a second storage capacitor 14, and.a second resistor 15. The'negative terminal of the voltage regulatordischarge device 11 is connected to the negative terminal of the powersupply output which is preferably grounded and the positive terminal ofthe discharge device.

nected to ground. The controlgrid'ld is connected to a resistor 17, theother terminal of which is connected to a'tap 18 on a bleeder resistor19, connectedacross the power supply output terminals 2. A filtercapacitor 20is connected between the control gri'd16 and the positive.output terminal. The screen grid 21'is connected. to the junctionbetween resistor 13 and resistor 15'. The sup pressor grid 22 isconnected to the cathode 10L The time delay circuit includes-a resistor23, a capacitor" 24, a gaseous discharge device 25 and'resistor'9.Theresistor 23 is connected in series with' the'capacitor 24 across theoutput terminals 2. of the power supply. The gaseous discharge device 25is connected between thegrid 7, and

the junction of the resistor 23 and the capacitor 24. Re-

sister 9 is connected betweenv anodes and grid 7.

Considering now the operation oftheembocliment. of

the invention shown in the drawing, the: direct-current source 1supplies a voltageto the. load. 2 throughithe: variable resistance 3.The magnitude ofthe. voltage. supplied to the loadis dependent. on thecondition. ofconaavsaars ductivity of the variable resistance 3, thecontrol grid of which receives a control voltage from the control armplifier 4. The control amplifier 4 develops a voltage proportional tothe output voltage but in inverse phase thereto, which on application tothe variable resistance 3, tends to maintain the output voltageconstant.

Examination of the drawing will indicate the manner of obtaining thiscontrol voltage. The control grid 16 of the control amplifier isconnected through a filter, comprising resistor 17 and capacitor 20 to atap 18 on the bleeder resistance 19, thereby obtaining a voltage whichis directly proportional to the output voltage appearing across theload. The voltage applied to the cathode of the control amplifier is astabilized reference voltage.

It is obtained from a voltage regulator discharge device 11 which issupplied with energizing potentials through voltage dropping resistorsand 13, the voltages supplied thereto being filtered by storagecapacitors 12 and 14, connected respectively at the voltage regulatordischarge device and at the junction of the two resistors. The screengrid 21 also receives a positive potential from this circuit, beingconnected to the junction of the resistors 13 and 15. It may now be seenthat the voltage between the control grid and the cathode is equal tothe difference between a desired fraction of the output voltage and areference voltage, and that any variation of the output voltage withrespect to the reference voltage will produce a corresponding changeacross the output load resistor 9 of the control amplifier 4. Thisoutput voltage will be in inverse phase to the output voltage variationsso that application of this voltage to the control element 7 of thevariable resistance 3 will tend to maintain the output voltagesubstantially constant. The adjustment of the tap 18 upon the bleederresistor 19 makes it possible to apply a differing fraction of theoutput voltage to the control amplifier discharge device 4, therebypermitting the production of different output voltages.

Connection of the load resistor 9 of the control amplifier to thepositive terminal of the direct current source permits a uniformly highsensitivity voltage control. In addition to the increased potentialavailable at this terminal over that available at a connection to theoutput of the power supply, the available potential is not subject toreduction whenever the power supply is operated to produce a low outputvoltage. The connection shown, consequently permits the use of a largeplate load resistance for the control amplifier device 4, permittinghigher gain operation, without the gain of the amplifier being adverselyaffected when low output voltages are desired. In addition, during thewarm-up period, this connection tends to apply a high positive potentialacross the gaseous discharge device 25 used to initiate operation of thetime delay circuit, the operation of which will now be described.

Prior to energization of the power supply, the capacitor 24 is in adischarged condition, the resistor 23 and the bleeder resistor 19providing a discharge path for it. After energization of the powersupply, upon the first appearance of a potential exceeding theionization potential of the gaseous discharge device 25, the dischargedevice 25 fires, thereby presenting a conductive path between thecapacitor 24, normally at zero potential, and the control grid ofvariable resistance 3. In this manner bias potential is supplied to thecontrol grid 7 of the variable resistance 3. The magnitude of this biaspotential is limited to the sum of the operating potential of thegaseous discharge tube 25 and the potential of the capacitor 24. Whenthe variable resistance 3 begins to conduct and its cathode voltagebegins to rise, the bias thus applied by the capacitor 24 through thegaseous discharge device 25 is effective to reduce the conductivity ofthe variable resistance to a value sufiicient to prevent an excessiveoutput voltage at terminals 2. The maximum value which the outputvoltage reaches is dependent on the current flowing through tube 3 andmay be con- 4 trolled by choice of a suitable bleeder resistance. Thebias being supplied from the capacitor 24 continues until the controlamplifier 4 is fully warmed up and capable of applying the usual controlpotentials to the variable resistance tube. After the control amplifier4 has taken control, the current supplied to the amplifier throughresistor 9 and the increasing voltage appearing across the capacitor 24due to charging, reduces the potential across the gaseous dischargedevice 25. When the deionization potential of discharge device 25 isreached, the time delay circuit is no longer efiective to control thevariable resistance and it has no further eifect upon the gain of thecontrol amplifier 4, since it is isolated by the substantially infiniteimpedance of the deionized gaseous discharge device 25.

The duration of the protection period may be controlled by a suitablechoice of the values for resistor 23 and capacitor 24. When time delayon the order of 4 or 5 seconds is desired, the resistance may be on theorder of 100,000 ohms and the capacitor may be of approximately 40microfarads. The conduction of the gaseous discharge device 25 does notappreciably efifect the charging rate since the currents involved aresubstantially less than the normal charging current flowing through thecharging resistor 23. The gaseous discharge device 25 should be chosenso as to have an ionization voltage and deionization voltage ofsubstantial separation, both preferably being greater than the usualrange of control potentials applied to the variable resistance tube soas not to restrict the operation of the variable resist ance 3. Anionization voltage of the order of 180 volts and a deionization voltageof approximately volts is suitable when a conventional variableresistance device such as a 6AS7G type discharge device is employed.

The invention thus provides an effective warm-up period control in avoltage regulated power supply and at the same time permits undisturbedhigh gain operation of the component control voltage amplifier so as tomaintain the control substantially as effective at one output setting asat another.

In carrying out the invention it is, of course, apparent that variationsin the embodiment shown may be made without departing from the spirit ofthe invention. It is contemplated by the appended claims to cover anysuch modifications as fall within the true spirit and scope of theinvention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A voltage regulated power supply comprising a source ofunidirectional voltage, a pair of output terminals for connection to aload, a variable resistance electric discharge device having an another,a cathode, a control grid, and heating means effective to bring saidvariable resistance device to conductivity within a relatively shortperiod of time, said anode being connected to the positive terminal ofsaid source and said cathode being conduc tively connected to one ofsaid output terminals, and a control electric discharge device havingheating means requiring a somewhat longer time than required for saidfirst heating means to bring said con trol device to conductivity, saidcontrol device being responsive to variations in voltage across saidoutput terminal and having an anode connected to said grid to apply saidvariations in inverse phase to said control grid to control theconductivity of said variable resistance device, a time delay circuitincluding a charging resistance and a capacitor joined and connected inseries in .the order recited between said cathode and the other of saidoutput terminals respectively, another resistance connected between thepositive terminal of said source and the anode of said control device, agaseous discharge device having a pair of electrodes, one of saidelectrodes being connected to said grid and the other of said electrodesbeing connected to the junction of said charging resistance and saidcapacitor, the elements of said delay circuit being proportioned tocause ionization of said gaseous discharge device from the time saidpower supply is energized up to the time said control device is renderedconductive and deionized thereafter whereby said grid is biased toreduce the conductivity of said variable resistance device during thetime said control device is inelfective in controlling the conductivityof said variable resistance device and said control device is operatedwith optimum effectiveness thereafter.

2. In combination, a source of unidirectional voltage, a load, anelectron discharge device including a cathode, a grid and an anode, theanode-cathode discharge path of said device being connected in circuitwith said source and said load to permit current to flow between saidsource and said load, an amplifier including an output load resistance,said amplifier being energized from said source and said load resistancebeing connected between said anode and said grid, a voltage dividercircuit connected in shunt with said load and in circuit with the inputof said amplifier to supply variations in voltage across said load tosaid amplifier, whereby the potential of said grid is varied in a mannerto maintain said load voltage substantially constant, another resistanceand a capacitance being joined and connected in series in the orderrecited between said cathode and the negative terminal of said source, agaseous discharge device having one terminal connected to said grid andthe other terminal connected to the junction of said other resistanceand capacitance, said resistance and capacitance being proportioned tocause a gradual rise in potential of said junction, said load resistanceand gaseous discharge device being proportioned to cause ionization ofsaid gaseous discharge when said unidirectional source is energizedthereby limiting the potential of said grid and the voltage supplied tosaid load and to cause deionization of said gaseous discharge device asthe potential of said junction rises to a predetermined value.

3. A voltage regulated power supply comprising a source ofunidirectional potentials, a variable resistance electric dischargedevice having two principal electrodes for unidirectional conductiontherein and a control element, output terminals for connection to a loadenergized by said source through a path including said principalelectrodes, an amplifier discharge device having the anode thereofconductively connected to said control element and connected through aload resistance to the positive terminal of said source, said amplifierdevice being arranged to supply to said control element a Voltage whichvaries inversely to the voltage at said output terminals, and a circuitfor reducing the conductivity of said variable resistance device for aninterval after said power supply is turned on, comprising a resistanceand capacitance connected together and connected in series in the orderrecited between the positive output terminal and the negative outputterminal, and a gaseous discharge device coupled between said controlelement and the junction of said last recited resistance andcapacitance.

4. A voltage regulated power supply comprising a source ofunidirectional potentials, a variable resistance electric dischargedevice having two principal electrodes for unidirectional conductiontherein and a control element, output terminals for connection to a loadenergized by said source through a path including said principalelectrodes, an amplifier discharge device having the anode thereofconductively connected to said control element and connected through aload resistance to the positive terminal of said source, said amplifierdevice being arranged to supply to said control element a voltage whichvaries inversely to the voltage at said output terminals, and a circuitfor reducing the conductivity of said variable resistance device for aninterval after said power supply is turned on, comprising a resistanceand capacitance connected together and connected in series in the orderrecited between the point in said path on the output side of saidvariable resistance device of positive potential and the negativeterminal of said source, and a gaseous discharge device coupled betweensaid control element and the junction of said last recited resistanceand capacitance.

5. In combination, a source of unidirectional poten tials, a variableresistance electric discharge device having an anode and a cathode forunidirectional conduction therein and a control element, said anodebeing coupled to the positive terminal of said source, an amplifierdischarge device having the anode thereof conductively connected to saidcontrol element and connected through a load resistance to the positiveterminal of said source, said amplifier device being arranged to supplyto said control element a voltage which varies inversely with thevoltage between said cathode and the negative terminal of said source,and a circuit for reducing the conductivity of said variable resistancedevice for an interval after energization of said power supply,comprising a resistance and capacitance connected together and connectedin series in the order recited between said cathode and the negativeterminal of said source, and a gaseous discharge device coupled betweensaid control element and the junction of said last recited resistanceand capacitance.

References Cited in the file of this patent UNITED STATES PATENTS

